1/* SPDX-License-Identifier: GPL-2.0-only */
2/* Copyright (c) 2014-2015 The Linux Foundation. All rights reserved.
3 *
4 * A call to __dcc_getchar() or __dcc_putchar() is typically followed by
5 * a call to __dcc_getstatus().  We want to make sure that the CPU does
6 * not speculative read the DCC status before executing the read or write
7 * instruction.  That's what the ISBs are for.
8 *
9 * The 'volatile' ensures that the compiler does not cache the status bits,
10 * and instead reads the DCC register every time.
11 */
12#ifndef __ASM_DCC_H
13#define __ASM_DCC_H
14
15#include <asm/barrier.h>
16#include <asm/sysreg.h>
17
18static inline u32 __dcc_getstatus(void)
19{
20	return read_sysreg(mdccsr_el0);
21}
22
23static inline char __dcc_getchar(void)
24{
25	char c = read_sysreg(dbgdtrrx_el0);
26	isb();
27
28	return c;
29}
30
31static inline void __dcc_putchar(char c)
32{
33	/*
34	 * The typecast is to make absolutely certain that 'c' is
35	 * zero-extended.
36	 */
37	write_sysreg((unsigned char)c, dbgdtrtx_el0);
38	isb();
39}
40
41#endif
42